In the related art, as an optical scanning device installed in an electrophotographic image forming apparatus, an optical scanning device using a polygon mirror has been known (for example, see Patent Literature 1). In this optical scanning device, light emitted from a light source is reflected from a peripheral surface of a rotating polygon mirror and is scanned in a predetermined direction. The optical scanning device includes a polygon motor for rotating the polygon mirror, a driving substrate, and a housing for receiving these elements in addition to the polygon mirror.
The polygon motor is supported to the driving substrate and the driving substrate is fixed to a bottom wall part of the housing. In the driving substrate, electronic parts such as a connector and a driving IC are mounted.
The driving substrate is formed with a plurality of mounting holes, and the bottom wall part of the housing is formed with mounting target holes at positions corresponding to the mounting holes. The mounting target holes are coaxially formed with respect to a plurality of projecting bosses that project from the bottom wall part of the housing. The driving substrate is fixed by a coupling member passing through each mounting hole and each mounting target hole in a state of being supported to the plurality of projecting bosses.
In the image forming apparatus, there are cases where, in order to satisfy a wide range of user demands, a plurality of models having different processing speeds (that is, the number of sheets printable per unit time) are set. In order to change the processing speeds, it is necessary to change the rotating speed of the polygon motor. However, the possible number of rotations of the polygon motor is limited by performance and the like of a bearing. Therefore, the type of the polygon motor to be installed in an optical scanning device needs to differ in a low speed model and a high speed model.
However, when the type of the polygon motor is different, since a maker that manufactures the polygon motor is different, the arrangement configuration of the mounting holes of the driving substrate may also be different. In this case, when different housings are prepared for a plurality of substrates having different arrangement configurations of the mounting holes, the manufacturing cost may increase. In this regard, for example, in an optical scanning device disclosed in Patent Literature 1, a bottom wall part of a housing is formed with first mounting target holes for mounting a first substrate and second mounting target holes for mounting a second substrate having an arrangement configuration of mounting holes different from that of the first substrate. The first mounting target holes and the second mounting target holes are formed in first projecting bosses and second projecting bosses that project from the bottom wall part of the housing. Heights of the first projecting bosses and heights of the second projecting bosses are set to be identical to each other.